Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus using the same.
Description of the Related Art
In cameras including electronic image pickup element, such as digital cameras, reduction in size, weight, and costs have been advancing. For further reduction in size, weight, and costs, size reduction of bodies and size reduction of optical systems are additionally required.
Moreover, for example, there are two photographic needs for optical systems. The first photographic need is a need of taking a photo of a large building or a need of taking a ceremonial photo against a vast background. The second photographic need is a need of taking photos ranging from a wide view to a close up with a single photographic lens.
In order to satisfy the first photographic need, it is necessary to increase the angle of view of the optical system. In order to satisfy the second photographic need, it is necessary to increase the zoom ratio of the optical system. As the optical systems that satisfy the two photographic needs include, for example, a zoom lens having a half angle of view of 40 degrees or more and a zoom ratio of six times or more is available. The zoom lens having such specifications is usable in various photography scenes and therefore can be said to be an easy-to-use zoom lens.
In Japanese Patent Application Laid-open Nos. 2003-255228, 2009-282398, and H8-190051, zoom lenses including five lens units are disclosed. These zoom lenses include, in order from an object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power.